Fire-resistant hydraulic fluid compositions



nit ed States Patent ABSTRACT OF THE DISCLOSURE Improved water-in-oil emulsions are provided by the incorporation therein of from 1 to weight percent of a polyethylene having a molecular weight less than 100,000.

This invention relates to an improved lubricating composition and method of its preparation. In one aspect this invention relates to improved water-in-oil emulsions useful as fire-resistant hydraulic oils and metal-working oils and their method of preparation.

Hydraulic systems are being employed more and more extensively in industry to operate machinery from remote locations and with comparative ease. Various types of liquids have been employed as the operative fluid in these hydraulic systems; however, for one reason or another, these liquids have been found to lack required properties. Various oils, such as mineral oils, have found much favor in the past; however, many applications of hydraulic systems cannot tolerate leaks with such a pressure transmitting medium since the oil, under high pressure, may then find its way to heat and flame where explosion or combustion occurs. Hydraulic systems are used in metalworking and treating plants and leaks in the system have caused serious accidents in the past.

Water-in-oil emulsions have been tried in the prior art to provide a useful hydraulic oil that had the benefit of low flammability. As long as these emulsions remain unbroken with the Water uniformly dispersed throughout the oil in the form of fine particles, the fire resistance remains high. However, adequate stability of the emulsion in this respect has not been present in prior formulations. The water particles tend to agglomerate in clusters and to settle to the lower part of the reservoir, thereby imparing the fire resistance of the fiuid remaining in the upper part. In some cases, an upper layer of clear oil possessing no fire resistance whatsoever will result. In more severe cases, the water may coalesce into larger droplets which eventually will settle out and form a layer of free water on the bottom. In addition to impairment of fire resistance, the latter condition is objectionable in that free water may enter the circulating system and may cause corrosion of lines and working parts and rapid wear of pump parts due to lack of lubrication. It is essential, therefore, that the water particles be dispersed in the oil so that good lubricity is obtained. It is further essential that the water particles be small and uniformly distributed throughout the oil to keep corrosion tendency to a minimum and provide the minimal amount of wear.

Several water-in-oil emulsions have met with some success in that they have eliminated or mitigated fire haz ards present in such operations. They have further met with some success in that they have controlled wear of moving parts to a considerable degree although they do not possess the antiwear properties of compounded mineral oils containing no water. It has been desired to improve the wear resistance of these water-in-oil emulsions up to the level of mineral oil and intensive investigations have been made to find a satisfactory additive system capable of maintaining highly stable Water-in-oil emulsions with high wear resistance. Furthermore, in many ice instances, prior emulsion lubricants have been limited to operating hydraulic systems at low to moderate temperature, e.g., at temperatures below F. There are, however, many occasions where operating temperatures exceed 150 F. by a considerable margin. An example is the coal mining industry where mining machinery must operate-in close quarters. In order to hold dimensions of hydraulic equipment to a minimum, capacity of the cooling system is restricted with the result that operating temperatures often exceed 150 F. In many cases, the system operates at F. and in some cases even higher. While stability is important at these temperatures, it is even more important to prevent wear from being excessive at these elevated temperatures.

An object of this invention is to provide an improved composition for use as an hydraulic oil.

A further object of this invention is to provide an improved composition having fire-resisting properties for use as an hydraulic oil.

A further object of this invention is to provide an improved stable water-in-oil emulsion having fire-resisting properties for use as an hydraulic oil.

A further object of this invention is to provide an improved stable water-in-oil emulsion having fire-resisting properties for use as an hydraulic oil and having stability under high temperature use conditions.

A further object of this invention is to provide an improved water-in-oil emulsion which causes minimum wear of moving parts.

Other aspects, objects and the several advantages of this invention are apparent from a study of the disclosure and the appended claims.

In accordance with this invention I have discovered that a Water-in-oil emulsion having good lubricating properties can be prepared by emulsifying a mixture of water and oil with a polyethylene. More specifically, I have discovered that the lubricating properties of water-in-oil emulsions can be improved by the addition of 1 to 10 weight percent polyethylene based on the finished emulsion either to the oil phase prior to emulsification, or as an aqueous emulsion to the water phase used in preparing the finished emulsion.

The term a polyethylene is intended to include both homopolymers and copolymers of ethylene having a weight average molecular weight of less than 100,000.

The oil used can be any mineral lubricating oil having a viscosity (SUS at 100 F.) of 50 to 1500, preferably 70 to 1250. The emulsifier used can be any known to the industry for forming water-in-oil emulsions, the sole restriction being that when the polyethylene is added as an aqueous emulsion the emulsifier present in this emulsion is compatible with that used for preparing the water-in-oil emulsion. The following tabulation of emulsifier compatibility is useful in determining the emulsifiers that can be used together:

Emulsifier for water-in-oil Emulsifiers compatible Emulsion: therewith.

Anionic Nonionic, amphoteric (basic), anionic.

Cationic Nonionic, amphoteric (acidic), cationic.

Nonionic Anionic, cationic,

amphoteric, nonionic.

Amphoteric Do.

The polyethylenes that can be used are any available to the industry. When added to the oil phase prior to emulsification, it is preferably in the form of very finely divided materialsuch as 5 to 10 microns. When added as an aqueous emulsion to the water phase used in preparing the finished emulsion, an emulsifiable polyethylene is used. Mixtures of different polyethylenes can be used, and addi- Weight percent Oil 28-97 Emulsifier 1-10 Polyethylene 1-10 Water 1-70 The following examples are presented to further illustrate this invention.

Examples Water-in-oil emulsions were prepared using the following materials:

(1) Oil: A parafiinic, Mid-Continent SAE 10 oil having a viscosity of 120 SUS at 100 F.

(2) Emulsifier: A calcium petroleum sulfonate prepared by the process of US. 3,135,693.

(3 Polyethylenes:

A. A nonionic aqueous emulsion of polyethylene having a solids content of 40.8 percent. This emulsion was prepared by Spencer Chemical Company, and is identified as Poly EM. These emulsions are usually prepared with Polyethylene B or C, using known anionic, cationic, or nonionic-emulsifiers.

B. A wax-like polyethylene having the following properties:

Avg. molecular weight 1800 Melting point, F. 213-221 Viscosity at 284 F., cps 160 Density, g./cc. 0.93

This material is sold by Allied Chemical Corporation as A-C 629 polyethylene.

C. A wax-like polyethylene having the following properties:

Avg. molecular weight 2000 Melting point, F. 219-226 Viscosity at 284 F., cps. 180

Density, g./cc. 0.92

This material is sold by Allied Chemical Corporation as A-C 6 polyethylene.

D. A to 10 micron polyethylene having the following properties:

Density, g./cc. 0.965

Melt index 3 19.5

This material is sold by U. S. Industrial Chemicals Company as Ultrathene.

E. An ethylene-butene-l copolymer having the following properties:

Density, g./cc. 0.952 Melt index 310 1 ASTM E 2s-51'1.

ASTM D 1505-601. 3 ASTM D 1238-57T, Condition E.

The emulsions were prepared in the following manner: The oil, emulsifier, and polyethylene were mixed, heated to about 150 -F., and added to the charge tank of a Manton-Gaulin colloid mill. Water was added while the oil phase was circulating through the mill at 150- 200 F. After water addition was complete, the statorrotor spacing of the mill was set at 0002-0005 inch and milling was continued for 2 to 5 minutes. When the aqueous polyethylene emulsion (Poly EM) was used, it was added to the water phase prior to milling.

Run N0 l 2 3 4 5 6 7 8 P y A-O A-C 629 Polyethylene Ultrathene.

Water Wear, m'crons l Yielding 5.1 weight percent polyethylene.

These data show that use of the water-in-oil emulsions of the invention containing polyethylene result in less wear than is obtained with either the base oil or with the emulsified base oil.

An oxidation inhibitor may be provided to prevent oxidative degeneration of the product in use which would otherwise bring about the formation of acid oxidation products. While many compatible oxidation inhibitors may be used, such as amine types, aminophenol types, and some phenolic inhibitor types, a preferred and convenient inhibitor, commercially available, is the Agerite Stalite of R. H. Vanderbilt Company (p,p-dioctyldiphenylamine). The oxidation inhibitor may be added in the amount of 0.1-5.0 percent by weight of the total composition or preferably about 0.25-1.5 percent by weight of the total composition.

Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope of the invention.

I claim:

1. A composition consisting essentially of an emulsion containing therein (a) a mineral lubricating oil having a viscosity of about 50 to 1500 Saybolt Universal Seconds at F, (b) calcium petroleum sulfonate, (c) a polyethylene having a molecular weight in the range of 1800 to less than 100,000, and (d) water and wherein said mineral lubricating oil is present in an amount in the range of 28 to 97 weight percent, said emulsifier is present in an amount in the range of 1 to 10 weight percent, said polyethylene is present in an amount in the range of 1 to 10 weight percent and said water is present in an amount in the range of l to 70 weight percent.

2. A composition according to claim 1 wherein said polyethylene has a molecular weight of 1800, and said mineral lubricating oil is a parafiinic, mid-continent SAE 10 oil having a viscosity of Saybolt Universal Seconds at 100 F.

3. A composition according to claim 1 wherein said polyethylene is selected from the group consisting of (1) a nonionic aqueous emulsion of polyethylene having a solids content of 40.8 percent; (2) a wax-like polyethylene having an average molecular weight of 1800, a melting point of 213-221 F. and a density, g./cc., of 0.93; (3) a wax-like polyethylene having an average molecular weight of 2000, a melting point of 219-226 F. and a density, g./cc., of 0.92; (4) a 5 to 10 micron polyethylene having a density, g./cc., of 0.965 and a melt index of 19.5 and (5) an ethylene-butene-l copolymer having a density, g./cc., of 0.952 and a melt index of 310.

References Cited UNITED STATES PATENTS 3,076,792 2/ 1963 Hollyday et al 25259 X 3,159,580 12/1964 Hammer et al 25275 LEON D. ROSDOL, Primary Examiner.

S. D. SCHWARTZ, Assistant Examiner. 

